Alrighty, I got parts in and on my lunch swapped the MAP and fuel pressure regulator out. it seemed fine, but when I applied vacuum to the nipple it made a weird "click" that the new one did not. I think whatever diaphragm that was in there was old and tired. The new map tested a bit more responsive/better when I compared it to the one I had on my truck already, but alas when I threw both those parts on and started it up it still had bad throttle response and still had the weird restart issue.

I'm running out of ideas, I have a new EGR on the way to see since my prev. experiment with a blockoff plate did not seal properly, if that doesn't work what else is there? Evap canister? is there an air temp sensor anywhere on these?(I read and searched and did not see any documentation saying it did or didn't have one).

Could it be the throttle kicker motor? it actuates and seems to work fine but I read that some people need to service them and give them new grease on the inside to make sure they stay fresh

 

Read over the FAQ section is all I have. There are 'common problems" listed there that may help solve you issue.

 

alrighty, well I have good news! the EGR seems to have solved about 80% of the problem! Upon comparison with the new EGR I got, it seems the valve was closing all the way, but there was a crack in the egr "manifold(?)" going into the intake which was obviously the biggest source of my issue. Now It does not surge when cold, starts up much stronger, and idles right around 900 after adjusting the stepper motor with the temp sensor and motor unplugged. (still a little high, probably the pcv if I had to bet so no big deal)

It still hesitates a bit too much for my liking when starting it up when it's warm, seems to take a solid 2-3 tries before it'll light off but I no longer have to wait 15-20 mins before being able to start it again so that is a huge win in my book and as particular as I am about how I want this thing to be dialed, it's 36 years old so... whatever at least it's not in the junkyard haha

Since I was mentally prepared to spend another couple hundred if this didn't work I will probably go ahead and replace the pcv, breather, and do another inspection of the vacuum hoses everywhere to quadruple check for vac leaks since it seems that is the root of my problems at the moment. Thank you all though for all the help

 

Good news! Maybe a thorough cleaning of the fuel system will get you the last 20%.

 

Perhaps, I replaced one of the injectors already and it has a new fuel pump, filter, and pressure regulator and I ran a couple cans of seafoam through it. I would be surprised if there's much more tuning the fuel systems needs but I'll def keep an eye on the other injector I didn't replace and make sure the throttle body stays squeaky clean.

I think I was mistaken originally in hindsight, I noticed the truck would start with carb cleaner and didn't find obvious vac leaks so I incorrectly assumed it wasn't getting enough fuel, when in fact it was just getting too much air, and still might be considering my idle is still a tiny bit on the high side. I was spoiled before with my jeep, it never gave me any running issues aside from the crank position sensor which was pretty easy to diagnose so I am def a bit rusty when it comes to doing diag like this

 

Not a fan of Seafoam. Look into ATS Chemical for their 505 fuel treatment if you decide to do another treatment. I think you can go to their website to order it. Not cheap, but is effective. They make an oil treatment as well. Excellent products for removing carbon buildup. Maybe measure your gas mileage to see if you're getting what you expect. Always a good sign for dirty/faulty injectors.

 

Noted, I know I before I fixed the egr I got about 15mpg with mixed driving and assuming I replace the pcv and any other misc vac leaks I fully expect/hope to maybe get 18-20 on the highway if I don't push it so I will keep that in mind and if the bank account lets me I may run that treatment before my roadtrip to TX, thanks for the tip!

 

Good news for you then.
I was looking at the FAQ section and notice (maybe I'm misremembering?) there is no longer a post about the plenum leak issue. Oil at the bottom of the intake if you look down the TB is the one of the tells. There was a list if the symptoms I do not remember. It was what was wrong with mine when I got it.

 

Yeah, I'm not sure what the 3.9 gets. My 5.2 gets 15 mpg with mixed driving. Doesn't improve dramatically with highway either. 16.5ish. You'd think the 3.9 would be better but I'm kinda thinking I heard it isn't much better.

 

MPG's used to bug me a lot. When I got this thing v6, the gas gauge did not work and I ran out of gas after just over 150 miles on a 22 gallon tank. That worked out to about 7mpg. I did the plenum also fixed gauge and took a long drive using up a full tank on the hwy and got 19mpg's. I only do hwy about 5 miles or so and mainly in town driving since and I get 15ish sometimes less. There was a guy on here who used to post that he got 23mpg. I don't remember if he had the v6 or v8.